不同浓度和形态磷处理下内生真菌感染对高羊茅的影响

Abstract

Phosphorus( P) is one of the essential nutrient elements for plant growth and development,but the effective phosphorus in the soil is often low. Many studies showed that mycorrhizal fungi could improve the ability of the host plants in using sparingly soluble phosphate fertilizer. Similar to mycorrhizal fungi,endophytes are symbiotic with plants to some extent. Cool-season grasses and fungal endophyte Neotyphodium coenophialum are reported to be mutualistic symbions. But reports on endophyte-related responses of grasses to P nutrition,particularly to P forms are limited. In this paper,endophyte-infected( EI) and endophyte-free( EF) tall fescue were used as materials and their ecophysiological response to different P levels and P forms were compared.The experiment was carried out in the greenhouse on the campus of Nankai University. There were three phosphate fertilizer treatments,i. e. application of sparingly soluble phosphorus [Ca3( PO4)2]fertilizer,water-soluble phosphorus[Ca( H2PO4)2-H2O]fertilizer and no addition of phosphorus fertilizer. Each treatment consisted of 5 pots of EI and 5 pots of EF tall fescue plants. In addition,N,P,and K fertilizer were applied with 300,100,and 150 mg /kg,respectively. At the end of the experiment,we noted the number of tillers and leaves,and measured the dry weight of the shoot and the root. Besides,we detected the content of total phenol and organic acid as well as the activity of acid phosphatase( Apase).When no P fertilizer was added,there was no significant difference in growth between EI and EF plants,and EI plants tended to perform worse than EF plants. When normal P fertilizer was supplied,EI plants had more tillers and leaves than EF plants,which may partly prove the viewpoint that the beneficial effect of endophyte infections usually occurs in high soil nutrients conditions.As for the responses to different phosphorus forms,we found that the root organic acid content and the acid phosphatase activity were significantly higher in the sparingly-soluble P conditions than in the water-soluble P conditions,while total phenol content of the root was similar between the two treatments. In the water-soluble P conditions,EI plants had both higher content of total phenol and more tillers,and leaves than EF plants,which indicated that the endophyte had certain contributions to shoot growth of the host plants. In the sparingly-soluble P conditions,EI roots had higher content of total phenol but lower content of organic acids than EF plants; meanwhile,endophyte infection just increased the root-shoot ratio of the host plants. This indicated that endophyte infection contributed little to the host plants in using sparingly-soluble P. Since we did not determine the root morphology of the experimental tall fescue,we could not rule out the possibility of endophyte infection changing the root morphology of tall fescue without changing the root biomass,which needs further study. Besides,whether endophyte infection is beneficial to the host plant in the P-deficient condition depends on the host plant species or varieties. In a word,our experiment indicated that endophyte infection was more beneficial to host growth when water-soluble P was supplied.